1. Technical Field
The following description relates to one or more sheet feeders and image forming apparatuses provided therewith.
2. Related Art
A sheet feeder has been known that includes a friction member configured to contact a bottom one of stacked sheets in a sheet staking direction, so as to prevent such a failure that two or more sheets are fed together in a mutually overlapping state (hereinafter, the failure may be referred to as “multi feed”).
In the known sheet feeder, a feed roller is configured to apply a feeding force to the stacked sheets by rotating in contact with an upward-facing side of a top one of the stacked sheets in the sheet stacking direction. Hence, in the known sheet feeder, in order to prevent the multi feed, the friction member is provided to contact a downward-facing side of the bottom one of the stacked sheets in the sheet stacking direction, and thereby a frictional force is applied to the stacked sheets against the feeding force.
In the known sheet feeder, at a portion (hereinafter referred to as a supporting member) on which the friction member is disposed, a recessed section is formed such that the friction member is fitted thereinto. Further, the recessed section is formed with a depth as long as the thickness of the friction member, such that an upper surface of the friction member and an upper surface of the supporting member are at the same level. Thereby, it is possible to certainly establish contact between the friction member and the bottom sheet.
If the friction member is, in a simple form, disposed on the upper surface of the supporting member without any recessed section being formed, the upper surface of the friction member has to be higher than the upper surface of the supporting member. Namely, when the friction member is disposed on the upper surface of the supporting member, the upper surface of the friction member and the upper surface of the supporting member have to form a step-shaped boundary therebetween such that the downstream one of the two upper surfaces is higher than the upstream one thereof in a sheet feeding direction.
The friction member generally has a thickness more than that of a sheet to be fed (such as a recording sheet and a document sheet). Therefore, the aforementioned step-shaped boundary might cause an undesired situation such as empty feed and a wrinkled or folded sheet, as described below.